WORM 9D1473 - Caterpillar

Illustration 6 g03089540The air conditioning manual/auto mode switch (1) has a normally open contact and a normally closed contact. The contacts provide switch to ground inputs to the ECM to indicate the position of the switch. When in manual mode the A/C is activated. When in auto mode, the ECM determines if the A/C should be activated.High/Low Pressure Switch
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High-pressure switch
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Low-pressure switch
Illustration 9 g06082059High/Low pressure switch, used to prevent unwanted high pressure, and low-pressure conditions on the outlet of the A/C compressor. Low-pressure switch, used to prevent unwanted low-pressure conditions on the inlet side of the A/C compressor. Both the high/low and low-pressure sensors prevent operation of the A/C compressor during conditions of overcharge of the refrigerant and undercharge of the refrigerant.The air conditioning low-pressure contact at the ECM monitors the voltage state of the high and low-pressure cutoff switches for the air conditioning. The switches are set up in series from a power source. The switches close and allow power to pass when the pressure in the high pressure and low pressures air conditioning loops is high exceeds the actuation pressure for the switch. If both switches have been actuated, both switches are closed and the ECM contact is pulled to a low or ground voltage state. If either switch has not been actuated, the ECM contact is pulled to a high-voltage state.HVAC Evaporator Thermostat Switch
Illustration 10 g06081838The HVAC evaporator temperature sensor is a two-wire passive temperature sensor. The sensor sends an analog signal to the implement ECM indicating evaporator temperature. The sensor is a negative coefficient thermistor. The resistance range for the sensor is 33,650 ohms at −40° C (−40° F) to 18.6 ohms at 150° C (302° F). The sensor is used to determine evaporator temperature.Outputs
Condenser Fan Relays
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Relay schematic shows relay in the DEENERGIZED position.
The condenser fan relays control the operation of the condenser fans. The relay is activated by the ECM when the air conditioning system is active. When the relay is activated, the relay allows power to flow to the condenser fans. When the ECM has not activated the relay, power is not allowed to flow to the condenser fans.Clutches
HVAC A/C Compressor Clutch
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(3) Magnetic clutch and pulley assembly
(4) Coil assembly
(5) Drive plate
(6) Bearing
(7) Compressor shaftThe Implement ECM energizes the air conditioning clutch when the operator requests air conditioning and all the conditions have been met.The compressor is driven by the engine. A belt connects the engine to the clutch and pulley assembly (3). The pulley assembly is on the clutch. The drive plate (5) is fastened to the shaft of the compressor. The clutch and pulley assembly (3) turns on the bearing (6). The clutch and pulley assembly (3) are not connected to the shaft (7). The electric current from the thermostat controls a magnetic field in the coil assembly (4).The magnetic field pulls the drive plate (5) against the clutch and pulley assembly (3). The clutch and the pulley assembly (3) turns the shaft (7) that operates the compressor. When the